Re: Remote antenna for handheld VHF radio?
Generally speaking a fixed antenna is always better for 2 reasons. Generally speaking.
One is they are typically higher than the handheld. VHF is line of sight communication, so the higher the stations are the better off the tx and rx operations will be.
The other reason is antennas are polarized. That is they transmit in a radiating patter from the top(normally). To imagine this think of an antenna standing vertical. Now imagine a huge doughnut around that antenna. This is your transmission plane of the antenna. A antenna with a high gain will have a doughnut that is smooshed down and spread apart. A lower gain will have a doughnut that is fatter, but not as far across. Handhelds are typically of the second lower gain antennas. The reason is this. Imagine that "doughnut" extending miles out around the boat. Now remember that the antenna will always transmit on this "doughnut" and this doughnut will always remain perpendicular to the antenna. As the boat pitches and rolls, so does the doughnut and thus it may become in contact with the water, thus loosing your signal strength.
With lower gain antennas like those on handhelds the signals radiates on a nice big fat doughnut, so if you hold the radio at an angle while using it, the signal is still reaching out in all directions, the down fall here is the beam is not focused for distance.
Now take that same amount of power and tx through a fixed mount antenna with say 6db of gain. Using that same amount of power your tx beam is now focused and will reach farther out. But the antenna is more suspect able to tx loss if the antenna is not vertical.
This is the same reasoning on runabouts you'll see higher gain antennas used(6-8db) but on sail boats where the antenna is mounted way up high on the mast where the boats movement is exaggerated you'll see lower gain antenna(2-4 maybe even some 6db gain)
That's a over simplified explanation, I hope it didn't confuse you too bad.
One final thought, if the boat goes down, a fixed mount would be attached to the vessel, and attached to your radio.
5 miles out, I would stick with the stock antenna myself. It should be enough in the even of an emergency to hail someone.
Bill
